Retrokits RK-004 MIDI/Sync hub │MyVolts 5-way Boutique USB - haQ attaQ 213 - YouTube
RK-005 and Teenage Engineering OP-1 Support - Retrokits
RK-004 - Retrokits RK-004 - Audiofanzine
Retrokits - Here's how to connect the #rk004 to the #beatsteppro. Looping through the power on the side of the RK-004 still allows you to use the Beatstep Pro on another USB